1. Technical Field
The present invention is directed toward elongate plastic member assemblies and, more particularly, toward a peelable assembly of a plurality of intravascular tubes or plastic coated wires, a method of making the assemblies and an apparatus for making the assemblies.
2. Background Art
A variety of intravascular tube assemblies are known in the art. One such assembly consists of a number of elongate plastic tubes arranged in parallel, the tubes being joined to adjacent tubes along their entire length by an integral web of the plastic tube material. One such structure is disclosed in Hilderbrandt, U.S. Pat. No. 3,836,415.
Prior art tube assemblies are typically formed through integral extrusion. Integral extrusion, however, has several limitations. Most significantly, integral extrusion has proven to be a relatively expensive procedure. In addition, integral extrusion limits the shapes the tube assembly can take. For example, it is not possible to integrally extrude a coil tube assembly with individual coils of the assembly joined to adjacent coils. In addition, it is very difficult, if not commercially impractical, to join adjacent tubes at intervals along their length by conventional integral extrusion techniques.
One alternative method to integral extrusion for joining adjacent tubes in a tube assembly known in the prior art is the use of a plastic solvent which softens and melts an exterior peripheral surface of adjacent tubes. After application of the solvent, the tubes are placed in their desired adjacent positions, and upon evaporation of the solvent, a fluid resistant bond is formed between adjacent tubes. This process has two advantages over extrusion. First, it provides a method for joining tubes into an assembly at intervals along their lengths, as opposed to continuously. Second, the solvent process permits formation of tube assemblies such as coils. The use of solvents, however, is not without serious disadvantages. The solvents tend to emit noxious fumes which are dangerous to assembly workers. Also, the use of solvents creates hazardous waste disposal problems. The application of the solvents must be closely controlled so as to prevent application of too little or too much solvent, resulting in improper bonding of the tubes into an assembly or erosion of the tubes comprising the assembly. Finally, the use of solvents is undesirable because residual solvents can be harmful to users of the assembly--particularly where the assemblies are used in the medical field for transporting therapeutic fluids.
Durakis et al., U.S. Pat. No. 3,316,134, discloses a different method for joining elongate plastic members. In this method, parallel elongate plastic members are run over a heater element and then compressed together by a pair of rimmed wheels to form a joining web. This method requires joining adjacent elongate plastic members along their entire lengths. This method also does not permit the simultaneous joining of multiple elongate plastic members. Moreover, this method is not suitable for joining hollow elongate plastic members such as intravascular tubes, because the tubes may become deformed when run through the rimmed wheels. This method is also not satisfactory for producing assemblies such as coils.
The present invention is directed toward overcoming one or more of the problems discussed above.